Corrosion prevention method and composition



United States Patent of a-sulfonate type b'orrosioninhibitor'and formaldehyde lee gether or alternatively, they maybe added separately'to the well fluid. The resulting crude from the well, after separation of the brine by conventional methods, displays favorable corrosion inhibiting properties when transported through connecting pipe lines to the refinery.

By a sulfonate type corrosion inhibitor, I mean those inhibitors depending on a sulfonate base content for'corrosion inhibiting activity. Suitable inhibitorsinclude, but are not limited to, for example, neutralized hydrocarbonsoluble or mahogany petroleum sulfonic acids with as alkali and alkaline earth metal and ammonium mahogany sulfonates, which are oil-soluble types; neutralized hydrocarbon-insoluble or green petroleum sulfonicacids such as the salts of hydrocarbon-insoluble petroleum sulfonic acids and at least one aliphatic amine having froml2 to 30 carbon atoms'per molecule described in the pending to well fluids effectively provides improved protection against rusting or corroding .o'fzthefmetallic equipment in the well. ,The crude .oilso produced also possesses favorable rust-inhibiting properties when transported through connecting pipelines to the refinery. e j

Some degree of corrosion takes place in themetallic equipment, particularly iron, steel and ferrous alloy equipment, of practically all oil wells and in certain environments, corrosion may reach costly proportions. The casing, tubing, sucker rods and lead lines are particularly subject to corrosive elfectsr The sucker rods and sucker rod boxes operate under heavy load conditions and are especially susceptibleto failure by corrosion fatigue. As a result of corrosion, costs may be greatlyincreased because of the necessity of pulling tubing and sucker rods for repair or replacement. Indirect costs in terms of production losses while shut down for repair or replacement of rods, tubing, or other equipment may also prove to be considerable. The most effective method of corrosion control appears to reside in the use of chemical inhibitors. Such chemicals have a distinct advantage over other methods in that all parts of the well fluid system can be protected. Sulfonate type corrosion inhibitors, for example, ammonium mahogany petroleum sulfonate, are particularly "widely used for this purpose. Often, however, in the use of the sulfonate type inhibitors in actual field practice, the effectiveness of the inhibitor is satisfactory for a period and then suddenly decreases and extensive. corrosion damage occurs. Increasing the concentration of the inhibitor does not improve the anti-corrosive effect and .the corrosive action can only be stopped type inhibitor. p

I have found that the introduction of a' sulfonate type corrosion inhibitor and formaldehyde into oil well fluids surprisingly provides improved protection against corrosive action on metallic surfacesin'contact withthe well fluids compared to the used the sulfonate type inhibitor or formaldehyde alone. Moreover, the anti-corrosive action remains effective for very satisfactory lengths of time. The sulfonate type inhibitor and formaldehyde in combination cooperate to provide improved protection against corrosive action on metallic equipment in contact with well fluids. Synergistic action is obtained in that improved protection is provided over that which would be expected from the independent effects of the sulfonate type inhibitor and formaldehyde. For example, the cor-' rosive attack on a. steel surface-v is significantly reduced by more than the sum of the independent effects of an inhibitor and formaldehyde.

According to my invention, the inhibitor and formaldehyde are added to the well fluids by conventional methods, usually by merely injecting the desired amount down the annulus between the production tubing and the casing. The inhibitor and formaldehyde are added toapplication Serial No. 334,979, fiIed'February'S, 1953, of Robert L. Lothring er, now abandoned; and oil-soluble ammonianeutralized sulfonated mixtures of polyalkylated benzenes, i.e., the bottoms produced in the manufacture of monododecyl benzene (Neolene) which comprise'didodecyl benzene along with other polyalkylated benzenes, as described in pending application Serial No. 218,709, filed March 31, 1951, of Thomas G.'Wisherd, now US. Patent No. 2,671,757. Preferably, the sulfonate type inhibitor is an oil-soluble type.

The combination of the inhibitor and formaldehyde I is used inamounts ranging from about 1 to 50 pints per by "changingto a 'non-sulfonate 1,000 barrels of well fluid, i.e., crude oil and brine. Generally, a proportion of about 1 part of sulfonate inhibitor to about 0.1 to 10 parts of formaldehyde is satisfactory. For example, about 20 pints of the combination per 1,000 barrels of well fluid in a proportion of 1 part of inhibitor to 5 parts of formaldehyde are effective for oil well treatment. The actual amount of inhibitor and formaldehyde employed within the above range is ordinarily directly related to the corrosiveness of the well fluid, the resistance of the metallic surfaces to corrosion and the production rate. In particular, flow interruptions and varying temperature and pressures are capable of affecting corrosion considerably. Of course, the actual measure of corrosion, and therefore regulation of the amount employed, can be determined in the last analysis by the actual deterioration of the physical condition of the metallic surfaces involved. However, it may not be practical to rely on such physical inspections since the damage is then already effective. Accordingly, metal test blanks may be used for insertion into the well fluid stream and removed and examined at periodic intervals. Direct measurement of the well fluid acidity is also possible or a measure of the iron content may be made since this is an indication of the metal lost through corrosion.

Formaldehyde and a sulfonate type inhibitor and the combination were tested in actual well practice in oil wells in eastern Kansas. In one test, the use of formaldehyde 4% months while the use of the inhibitor and formaldehyde reduced tubing jobs to only 2 in a 9 month period. Thus, the combination produces improved results as con'ipared to the independent effects of the inhibitor or formaldehyde alone.

-I claim:

1. In the production of oil from wells wherein well fluid is withdrawn from an oil well in contact with metallic surfaces, the method of reducing the corrosive action on such metallic surfaces in contact with said well fluid which comprises introducing into the well fluid a corro-' sion inhibitor selected from the group consisting of neutralized mahogany petroleum sulfonic acid and neutralized sulfonated polyalkylated benzene bottoms produced in the manufacture of monododecyl benzene, and formaldehyde; said inhibitor being employed in a proportion of about 1 part to about 0.1 to 10 parts of formaldehyde.

2. In the production of oil from wells wherein well fluid is withdrawn from an oil well in contact with metallic surfaces, the method of reducing the corrosive action on such metallic surfaces in contact with said Well fluid which comprises introducing into the well fluid a neutralized mahogany petroleum sulfonic acid corrosion inhibitor and formaldehyde.

3. In the production of oil from wells wherein well fluid is withdrawn from an oil well in contact with metallic surfaces, the method of reducing the corrosive action on such metallic surfaces in contact with said well fluid which comprises introducing into the well fluid ammonia neutralized sulfonated bottoms produced in the manufac ture of dodecylbenzene which bottoms consist essentially of dodecylbenzene and other polyalkylated benzenes and formaldehyde.

4. Crude oil to which favorable rust inhibiting properties have been imparted by the addition of a corrosion inhibitor selected from the group consisting of neutralized mahogany petroleum sulfonic acid and neutralizedsulfonated polyalkylated benzene bottoms produced in the a r: 4 manufacture of monododecyl benzene, and formaldehyde; said inhibitor being employed in a proportion of about 1 part to about 0.1 to 10 parts of formaldehyde.

5. Crude oil to which favorable rust inhibiting properties have been imparted by the addition of a neutralized mahogany petroleum sulfonic acid corrosion inhibitor and formaldehyde.

6. Crude oil to which favorable rust. inhibiting 'properties have been imparted by the addition of an ammonia neutralized sulfonated bottoms produced in the manufacture of dodecyl benzene, which bottoms consist essentially of didodecyl benzene and other polyalkylated benzenes, and formaldehyde.

References Cited in the file of patent Wells, article in The Petroleum Engineer, Reference Annual, 1951, pages B-86, B--8 8, B-90, B--92', B-94, B-96, and 3-98. 

1. IN THE PRODUCTION OF OIL FROM WELLS WHEREIN WELL FLUID IS WITHDRAWN FROM AN OIL WELL IN CONTACT WITH METALLIC SURFACES, THE METHOD OF REDUCING THE CORROSIVE ACTION ON SUCH METALLIC SURFACES IN CONTACT WITH SAID WELL FLUID WHICH COMPRISES INTRODUCING INTO THE WELL FLUID A CORROSION INHIBITOR SELECTED FROM THE GROUP CONSISTING OF NEUGRALIZED MAHOGANY PETROLEUM SULFONIC ACID AND NEUTRALIZED SULFONATED POLYALKYLATED BENZENE BOTTOMS PRODUCED IN THE MANUFACTURE OF MONODODECYL BENZENE, AND FORMALDEHYDE; SAID INHIBITOR BEING EMPLOYED IN A PROPORTION OF ABOUT 1 PART TO ABOUT 0.1 TO 10 PARTS OF FROMALDEHYDE. 